Antibacterial compositions

ABSTRACT

An antimicrobial composition which comprises an isothiazolone compound, suppresses decomposition of the isothiazolone compound and reduces irritation of skin caused by the isothiazolone compound is provided. The antimicrobial composition comprises an isothiazolone compound of the following formula [1] or formula [2] and an aminocarboxylic acid of the following formula [3] or a derivative thereof:                    
     wherein R 1  is hydrogen, alkyl, alkenyl, alkynyl or aralkyl; X and Y are each hydrogen, halogen or form a benzene ring with the carbon atoms at the 4- and 5-positions of the isothiazolone compound; M is a cation of an alkali metal, alkaline earth metal, heavy metal or amine; Z is an anion; a is 1 or 2; n is an integer; R 2  is hydrogen or alkyl; R 3  is C 1 -C 5  alkylene; R 4  is hydrogen or C 1 -C 5  alkyl; R 2  and R 4  form a heterocyclic group; and b is 0 or 1.

CROSS REFERENCE TO RELATED APPLICATION

This application is a United States National Phase Application under 35USC 371 of International Application PCT/JP99/04727 (not published inEnglish) filed Aug. 31, 1999.

TECHNICAL FIELD

The present invention relates to an antimicrobial composition. Moreparticularly, the present invention relates to an antimicrobialcomposition which comprises an isothiazolone compound, suppressesdecomposition of the isothiazolone compound and reduces irritation ofskin caused by the isothiazolone compound.

BACKGROUND ART

Isothiazolone compounds such as 5-chloro-2-methyl-4-isothiazoline-3-oneas a typical example exhibit an excellent antimicrobial property and arewidely used as slime control agents, bactericides, algaecides andfungicides in various systems such as cooling water systems, paper andpulp industry, coating materials industry, adhesive materials industry,treatments of cutting oils and sewage treatments. However, isothiazolonecompounds are very unstable and stability of agents containing thesecompounds must be improved in order to use the agents effectively.Therefore, various studies have been conducted on the improvement.

For example, in the specification of Japanese Patent ApplicationPublication Showa 54(1979)-23968, complexes of isothiazolone compoundswith metal salts such as calcium chloride and zinc chloride are proposedas a complex which have the activity for killing organisms, are usefulfor controlling various types of organisms, particularly microorganisms,and not easily decomposed in the presence of ordinary additives orcontaminating substances or in severe conditions and show excellent heatstability. In the specification of the U.S. Pat. No. 3,870,795, it isreported that isothiazolone compounds can be stabilized by suppressingdecomposition by addition of metal nitrates such as calcium nitrate andmagnesium nitrate or metal nitrites such as sodium nitrite and calciumnitrite to solutions of isothiazolone compounds.

In the specifications of Japanese Patent Application Laid-Open Nos.Showa 61(1986)-56174 and Showa 61(1986)-212576, stabilized solutions ofisothiazolone compounds prepared by addition of metal salts such ascopper chloride, sodium chloride, magnesium chloride and copper nitrateto solutions of isothiazolone compounds such as5-chloro-2-methyl-4-isothiazoline-3-one in propylene glycol,1,5-pentanediol or benzyl alcohol, are proposed.

However, the above agents and solutions had drawbacks in that stabilityof the isothiazolone compounds markedly deteriorates when the agents andsolutions are further diluted with water or organic solvents. In thespecification of Japanese Patent Application Laid-Open No. Heisei5(1993)-124917, a method for protecting isothiazolone compounds fromdecomposition using compounds containing sulfur such as L-cystine incombination with isothiazolone compounds is proposed. However, thismethod has a drawback in that L-cystine has a small solubility in waterand hydrophilic organic solvents and it is difficult to mix L-cystinewith isothiazolone compounds. Therefore, an antimicrobial compound whichsuppresses decomposition of isothiazolone compounds and shows excellentstability has been desired. Isothiazolone compounds often irritate skinand agents containing isothiazolone compounds must be handled withsufficient care. In the specification of Japanese Patent ApplicationLaid-Open No. Heisei 5(1993)-246807, compositions containing polycationcompounds such as polylysine and isothiazolone compounds are disclosed.However, it is known that these compositions do not show the effect ofsuppressing decomposition of the isothiazolone compounds.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an antimicrobialcomposition which comprises an isothiazolone compound, suppressesdecomposition of the isothiazolone compound and reduces irritation ofskin caused by the isothiazolone compound.

As the result of extensive studies to achieve the above object, it wasfound that specific aminocarboxylic acids and derivatives thereofexhibit the effect of stabilizing isothiazolone compounds and reducingirritation of skin caused by isothiazolone compounds. The presentinvention has been completed on the basis this knowledge.

The present invention provides:

(1) An antimicrobial composition comprising an isothiazolone compoundrepresented by general formula [1] or general formula [2] and anaminocarboxylic acid represented by general formula [3] or a derivativeof the aminocarboxylic acid:

wherein R¹ represents hydrogen atom, an alkyl group, an alkenyl group,an alkynyl group or an aralkyl group, X and Y each represents hydrogenatom or a halogen atom or form a benzene ring in combination with carbonatoms at 4- and 5-positions of the isothiazolone compound, M representsa cation of an alkali metal, an alkaline earth metal, a heavy metal oran amine, Z represents an anion forming, in combination with the cationrepresented by M, a compound having a sufficient solubility to form acomplex compound, a represents 1 or 2 and n represents an integerrequired for the anion represented by Z to satisfy a valence of thecation represented by M;

wherein R² represents hydrogen atom or an alkyl group having 1 to 5carbon atoms unsubstituted or substituted with carboxyl group, R³represents a linear or branched alkylene group having 1 to 5 carbonatoms, R⁴ represents hydrogen atom or an alkyl group having 1 to 5carbon atoms unsubstituted or substituted with carboxyl group, carbamoylgroup, hydroxyl group, phenyl group, hydroxyphenyl group, ureido group,methylthio group or 4-imidazolyl group, R² and R⁴ form a heterocyclicgroup unsubstituted or substituted with hydroxyl group or oxo group incombination with N—(R³)_(b)—C and b represents 0 or 1; and

(2) An antimicrobial composition according to (1), wherein thederivative of the aminocarboxylic acid represented by general formula[3] is a metal salt of the aminocarboxylic acid represented by generalformula [3]; a compound having a structure in which the aminocarboxylicacids represented by general formula [3] of one or more types are bondedto each other through a peptide bond or a metal salt of the compound; acompound having a structure in which the aminocarboxylic acidrepresented by general formula [3] is bonded to a differentaminocarboxylic acid through a peptide bond or a metal salt of thecompound; an N-acetyl compound of the aminocarboxylic acid representedby general formula [3] or a metal salt of the compound; or an amide ofthe aminocarboxylic acid represented by general formula [3].

Preferable embodiments of the present invention include:

(3) An antimicrobial composition described in any of (1) and (2), whichcomprises 0.1 to 10% by weight of the isothiazolone compound representedby general formula [1] or general formula [2]; and

(4) An antimicrobial composition described in any of (1), (2) and (3),which comprises the aminocarboxylic acid or the derivative thereofrepresented by general formula [3] in an amount by mol 0.1 to 50 timesthe amount by mol of the isothiazolone compound represented by generalformula [1] or general formula [2].

THE MOST PREFERRED EMBODIMENT TO CARRY OUT THE INVENTION

The antimicrobial composition of the present invention comprises anisothiazolone compound represented by general formula [1] or generalformula [2] and an aminocarboxylic acid represented by general formula[3] or a derivative of the aminocarboxylic acid.

In general formula [1] and general formula [2], R¹ represents hydrogenatom, an alkyl group, an alkenyl group, an alkynyl group or an aralkylgroup, X and Y each represents hydrogen atom or a halogen atom or form abenzene ring in combination with carbon atoms at 4- and 5-positions ofthe isothiazolone compound, M represents a cation of an alkali metal, analkaline earth metal, a heavy metal or an amine, Z represents an anionforming, in combination with the cation represented by M, a compoundhaving a sufficient solubility to form a complex compound, a represents1 or 2 and n represents an integer required for the anion represented byZ to satisfy a valence of the cation represented by M.

In general formula [3], R² represents hydrogen atom or an alkyl grouphaving 1 to 5 carbon atoms unsubstituted or substituted with carboxylgroup, R³ represents a linear or branched alkylene group having 1 to 5carbon atoms, R⁴ represents hydrogen atom or an alkyl group having 1 to5 carbon atoms unsubstituted or substituted with carboxyl group (—COOH),carbamoyl group (—CONH₂), hydroxyl group (—OH), phenyl group (—C₆H₅),hydroxyphenyl group (—C₆H₄OH), ureido group (—NHCONH₂), methylthio group(SCH₃) or 4-imidazolyl group:

R² and R⁴ form a heterocyclic group unsubstituted or substituted withhydroxyl group or oxo group in combination with N—(R³)_(b)—C and brepresents 0 or 1.

Examples of the isothiazolone compound represented by general formula[1] include 2-methyl-4-isothiazoline-3-one,2-ethyl-4-isothiazoline-3-one, 2-octyl-4-isothiazoline-3-one,5-chloro-2-methyl-4-isothiazoline-3-one,5-chloro-2-octyl-4-isothiazoline-3-one,4,5-dichloro-2-methyl-4-isothiazoline-3-one,4,5-dichloro-2-octyl-4-isothiazoline-3-one and1,2-benzoisothiazoline-3-one. Examples of the isothiazolone compoundrepresented by general formula [2] include complex compounds of theisothiazolone compounds represented by general formula [1] withmagnesium chloride, magnesium nitrate, copper chloride, copper nitrateand calcium chloride.

Examples of the aminocarboxylic acid represented by general formula [3]include glycine, alanine, β-alanine, valine, leucine, isoleucine,serine, threonine, asparagic acid, glutamic acid, asparagine, glutamine,sarcosine, citrulline, methionine, α-aminobutyric acid, β-aminobutyricacid, γ-aminobutyric acid, ε-aminocaproic acid, phenylalanine, tyrosine,histidine, proline, 4-hydroxyproline, 2-pyrrolidone-5-carboxylic acidand iminodiacetic acid.

As the compound having a structure in which the aminocarboxylic acidrepresented by general formula [3] is bonded through a peptide bond,compounds having a structure in which the aminocarboxylic acidsrepresented by general formula [3] of one or more types are bonded toeach other through a peptide bond are preferable. Examples of suchcompounds include glycylglycine, glycylglycylglycine,glycylglycyl-glycylglycine, glycylalanine, glycylasparagine,glycylleucine, glycylisoleucine, glycylphenylalanine, glycylproline,glycylsarcosine, glycylserine, glycylthreonine, glycylvaline,glycylglutamine, alanylalanine, alanylasparagine, alanylglutamine,alanylglycine, alanylphenylalanine, alanyltyrosine, β-alanylhistidine,polyasparagic acid and polyglutamic acid.

Examples of the N-acetyl compound of the aminocarboxylic acidrepresented by general formula [3] include N-acetylglycine,N-acetylalanine, N-acetyl-L-asparagic acid, N-acetyl-L-glutamic acid andN-acetyltyrosine.

Examples of the amide of the aminocarboxylic acid represented by generalformula [3] include glycineamide.

Examples of the metal salt of the compound represented by generalformula [3] and the derivatives thereof include lithium salts, sodiumsalts, potassium salts, calcium salts and magnesium salts.

The aminocarboxylic acids represented by general formula [3]occasionally include DL-compounds, L-compounds and D-compounds. Any ofDL compounds, L-compounds and D-compounds can be used in the presentinvention.

In the composition of the present invention, glycine and sodiumglutamate are preferably used as the aminocarboxylic acid represented bygeneral formula [3] and the derivative thereof. Glycine and sodiumglutamate have advantages in that the antimicrobial composition can beprepared rapidly since these compounds have great rates of dissolution,that the amounts by weight of these compounds are smaller when thesecompounds are used in a prescribed amount by mol relative to an amountby mol of the isothiazolone compound represented by general formula [1]or general formula [2] since these compounds have smaller molecularweights and that these compounds are readily available since thesecompounds are industrially produced in large scales.

In the composition of the present invention, the concentration of theisothiazolone compound represented by general formula [1] or generalformula [2] is not particularly limited. It is preferable that theconcentration is 0.1 to 10% by weight and more preferably 0.5 to 8% byweight. When the concentration of the isothiazolone compound representedby general formula [1] or general formula [2] is less than 0.1% byweight, the volume of the antimicrobial composition as a commercialproduct increases and there is the possibility that the product iseconomically disadvantageous in transportation and storage. When theconcentration of the isothiazolone compound represented by generalformula [1] or general formula [2] exceeds 10% by weight, there is thepossibility that stability of the antimicrobial composition is adverselyaffected.

In the present invention, the concentration of the aminocarboxylic acidrepresented by general formula [3] or the derivative thereof is notparticularly limited. It is preferable that the aminocarboxylic acid orthe derivative thereof is used in an amount by mol 0.1 to 50 times andmore preferably 1 to 10 times the amount by mol of the isothiazolonecompound represented by general formula [1] or general formula [2]. Whenthe amount of the aminocarboxylic acid represented by general formula[3] or the derivative thereof is less than the amount by mol 0.1 timesthe amount by mol of the isothiazolone compound, there is thepossibility that stability of the antimicrobial composition isinsufficient and decomposition of the isothiazolone compound tends totake place and that irritation of skin is enhanced. It is generallysufficient that the amount by mol of the aminocarboxylic acidrepresented by general formula [3] or the derivative thereof is 50 timesthe amount by mol of the isothiazolone compound or less. Stability ofthe antimicrobial composition or the effect of reducing irritation ofskin caused by the isothiazolone compound is not improved any more evenwhen the aminocarboxylic acid represented by general formula [3] or thederivative thereof is used in an amount by mol exceeding 50 times theamount by mol of the isothiazolone compound. When the derivative of theaminocarboxylic acid represented by general formula [3] is a polyaminoacid, it is preferable that the concentration of the derivative in theantimicrobial composition is 0.1 to 20% by weight.

The solvent used in the composition of the present invention is notparticularly limited as long as the isothiazolone compound representedby general formula [1] or general formula [2] and the aminocarboxylicacid represented by general formula [3] or the derivative thereof aredissolved in the solvent. Because the composition is often used in anaqueous system, water or a hydrophilic organic solvent is preferable asthe solvent. Examples of the hydrophilic organic solvent include amidessuch as dimethylformamide; glycols such as ethylene glycol, propyleneglycol, diethylene glycol and dipropylene glycol; glycol esters such asmethylcellosolve, phenylcellosolve, diethylene glycol monomethyl etherand dipropylene glycol monomethyl ether; alcohols having 8 or lesscarbon atoms; and esters such as methyl acetate, ethyl acetate,3-methoxybutyl acetate, 2-ethoxyethyl acetate, 2-ethoxypropyl acetateand propylene carbonate. It is preferable that pH of the antimicrobialcomposition of the present invention is 7 or less. It is more preferablethat pH of the composition is 2 to 5 to improve stability of theisothiazolone compound.

The antimicrobial composition of the present invention may furthercomprise corrosion inhibitors, scale inhibitors, antimicrobial agentsother than the isothiazolone compounds, defoaming agents, surfactantsand algicides where necessary.

Examples of the corrosion inhibitor include tolyl triazole,benzotriazole, methylbenzotriazole, molybdic acid, tungstic acid,silicic acid, nitrous acid, 2-phosphonobutane-1,2,4-tricarboxylic acid,hydroxy-ethylidenediphosphonic acid, hexametaphosphoric acid,tripolyphosphoric acid, orthophosphoric acid, salts of these compounds,zinc chloride, zinc chloride hydrochloride, zinc sulfate, zincligninsulfonate and hydrazine.

Examples of the scale inhibitor include polyacrylic acid, copolymers ofacrylic acid and 2-hydroxyethyl methacrylate, copolymers of acrylicacid, 2-hydroxyethyl methacrylate and methyl acrylate, copolymers ofacrylic acid and allyl glycidyl ether or a derivative thereof,copolymers of acrylic acid and 2-hydroxy-3-allyloxy-1-propanesulfonicacid, copolymers of acrylic acid and isoprenesulfonic acid, copolymersof acrylic acid and vinylsulfonic acid, copolymers of acrylic acid andallylsulfonic acid, polymaleic acid, copolymers of maleic acid or maleicanhydride and isobutylene, copolymers of maleic acid or maleic anhydrideand styrenesulfonic acid, copolymers of maleic acid or maleic anhydrideand acrylic acid, copolymers of maleic acid or maleic anhydride and2-acrylamido-2-methylpropanesulfonic acid, copolymers of maleic acid ormaleic anhydride and pentenoic acid, copolymers of maleic acid or maleicanhydride and a fluorescent substance such as 5-allylbenzosuberenolsubstituted with allyl group, polyacrylamide, polyitaconic acid andsalts of these compounds.

Examples of the antimicrobial agent other than the isothiazolonecompounds include halogenated aliphatic nitro compounds such as2-bromo-2-nitro-1,3-propanediol and 2,2-dibromo-2-nitroethanol; estersof these compounds; dibromonitrilopropionamide; alkylene bisthiocyanatessuch as methylenebisthiocyanate; 1,4-bisbromoacetoxy-2-butene;hexabromo-dimethylsulfone; isophthalonitrile compounds such as5-chloro-2,4,6-trifluoroisophthalonitrile andtetrachloroisophthalonitrile; dimethyl dithiocarbamate;4,5-dichloro-1,2-dithiol-3-one;3,3,4,4-tetrachloroteterahydrothiophene-1,1-dioxide; triiodoallylalcohol; bromonitrostyrene; aldehyde compounds such as glutaraldehyde,phthalaldehyde, isophthalaldehyde and terephthalaldehyde;dichloro-glyoxime; benzaldoxime compounds such as α-chlorobenzaldoximeacetate and α-chlorobenzaldoxime; and 5,5-dimethylhidantoin.

Examples of the defoaming agent include silicone and non-siliconedefoaming agents. Examples of the surfactant include anionic, cationic,nonionic and amphoteric surfactants. Examples of the algicide includetriazine compounds such as ametryne.

The embodiments of the composition of the present invention includeantimicrobial compositions containing 0.1 to 10% by weight of theisothiazolone compound represented by general formula [1] or generalformula [2], 0.1 to 20% by weight of the aminocarboxylic acidrepresented by general formula [3] or the derivative thereof, 0 to 50%by weight of corrosion inhibitors, 0 to 50% by weight of scaleinhibitors, 0 to 30% by weight of other antimicrobial agents, 0 to 10%by weight of defoaming agents, 0 to 10% by weight of surfactants, 0 to10% by weight of algicides and 30 to 99% by weight of water or ahydrophilic organic solvent.

The antimicrobial composition of the present invention can be used in aconcentration suitably selected in accordance with the subject and theobject of the application. For example, when the composition is used forprevention of slime in a paper and pulp manufacturing system or in acooling water system, it is preferable that the concentration of theisothiazolone compound is 0.1 to 25 g/m³. When the composition is usedfor prevention of putrefaction of an emulsion of a synthetic resin, astarch paste, a starch slurry, a coating material or an oil for metalworking, it is preferable that the concentration of the isothiazolonecompound is 1 to 5,000 g/m³.

The antimicrobial composition of the present invention contains theisothiazolone compound and the aminocarboxylic acid or the derivativethereof, shows excellent stability under heating and for a long time,does not cause decomposition of the isothiazolone compound for a longtime, exhibits the excellent antimicrobial effect derived from theisothiazolone compound and can be easily handled due to decreasedirritation of skin caused by the isothiazolone compound.

EXAMPLES

The present invention will be described more specifically in thefollowing with reference to examples. However, the present invention isnot limited to the examples.

In the examples and the comparative examples, irritation of skin by anantimicrobial composition was evaluated in accordance with the followingmethod.

The screening test of a prepared antimicrobial composition with respectto the irritation of skin was conducted using three white rabbits (NewZealand white strain) for each composition. A portion of a normal skinof a rabbit was used for the test. An antimicrobial composition withoutdilution in an amount of 0.5 ml was added to a patch of gauze andapplied to the portion for the test. After the patch was kept at theportion for 4 hours, the patch was removed and the portion was washed.Irritation of the skin was visually observed after 1, 24, 48 and 72hours and recorded in accordance with the criteria described below. Thenumbers with respect to the erythema and edema were added and theobtained sums were averaged to obtain a primary index for skinirritation (P1I) which was in the range of 0 to 8.

Erythema and Eschar formation

0: no erythema

1: very slight erythema (barely perceptible)

2: well-defined erythema

3: moderate to severe erythema

4; severe erythema (beet redness) to slight eschar formation (injuriesin depth)

Edema formation

0: no edema

1: very slight edema (barely perceptible)

2: slight edema (edges of area well-defined by definite raising)

3: moderate edema (raised approximately 1 mm)

4: severe edema (raised more than 1 mm and extending beyond the area ofexposure)

Example 1

An ethylene glycol solution (ZONEN-F; manufactured by ICHIKAWA GOSEIKAGAKU Co., Ltd.) containing 11% by weight of5-chloro-2-methyl-4-isothiazoline-3-one and 1% by weight of2-methyl-4-isothiazoline-3-one in an amount of 5.0 parts by weight, 0.62parts by weight of glycine and 94.38 parts by weight of water were mixedto form a homogeneous solution and an antimicrobial composition wasprepared.

The prepared antimicrobial composition contained glycine in an amount bymol twice the total amount by mol of5-chloro-2-methyl-4-isothiazoline-3-one and2-methyl-4-isothiazoline-3-one.

Additionally, 25 types of antimicrobial compositions were preparedusing, in place of glycine, alanine, β-alanine, DL-serine, DL-threonine,DL-asparagine, L-glutamine, sarcosine, DL-p-aminobutyric acid,γ-aminobutyric acid, DL-methionine, iminodiacetic acid, glycylglycine,glycylglycylglycine, glycylglycylglycylglycine, glycyl-L-glutamine,L-alanyl-L-glutamine, β-alanyl-L-histidine, pyrrolidonecarboxylic acid,N-acetylglycine, N-acetyl-L-tyrosine, sodium L-asparagate, sodiumL-glutamate, citrulline, phenylalanine or glycineamide as theaminocarboxylic acid represented by general formula [3] or thederivative thereof. An ethylene glycol solution (ZONEN-F; manufacturedby ICHIKAWA GOSEI KAGAKU Co., Ltd.) containing 11% by weight of5-chloro-2-methyl-4-isothiazoline-3-one and 1% by weight of2-methyl-4-isothiazoline-3-one in an amount of 5.0 parts by weight andthe aminocarboxylic acid represented by general formula [3] or thederivative thereof in an amount by mol twice the total amount by mol of5-chloro-2-methyl-4-isothiazoline-3-one and2-methyl-4-isothiazoline-3-one and water in an amount such that thetotal amount of the composition was 100.0 parts by weight were mixed toform a homogeneous solution.

The obtained 26 types of antimicrobial compositions were left standingat the room temperature for one month. The compositions remained astransparent liquids and no precipitates were found.

Comparative Example 1

An ethylene glycol solution (ZONEN-F; manufactured by ICHIKAWA GOSEIKAGAKU Co., Ltd.) containing 11% by weight of5-chloro-2-methyl-4-isothiazoline-3-one and 1% by weight of2-methyl-4-isothiazoline-3-one in an amount of 5.0 parts by weight and95.0 parts by weight of water were mixed to form a homogeneous solutionand an antimicrobial composition was prepared.

The prepared antimicrobial composition was left standing at the roomtemperature for one month. Yellow orange precipitates were formed in thecomposition.

The results of Example 1 and Comparative Example 1 are shown in Table 1.

TABLE 1 Aminocarboxylic acid or derivative thereof Appearance after onemonth Example 1 No. 1 glycine transparent liquid, no precipitates No. 2alanine transparent liquid, no precipitates No. 3 β-alanine transparentliquid, no precipitates No. 4 DL-serine transparent liquid, noprecipitates No. 5 DL-threonine transparent liquid, no precipitates No.6 DL-asparagine transparent liquid, no precipitates No. 7 L-glutaminetransparent liquid, no precipitates No. 8 sarcosine transparent liquid,no precipitates No. 9 DL-β-aminobutyric transparent liquid, noprecipitates acid No. 10 γ-aminobutyric transparent liquid, noprecipitates acid No. 11 DL-methionine transparent liquid, noprecipitates No. 12 iminodiacetic acid transparent liquid, noprecipitates No. 13 glycylglycine transparent liquid, no precipitatesNo. 14 glycylglycylglycine transparent liquid, no precipitates No. 15glycylglycylglycyl- transparent liquid, no precipitates glycine No. 16glycyl-L-glutamine transparent liquid, no precipitates No. 17L-alanyl-L-glutamine transparent liquid, no precipitates No. 18β-alanyl-L-histidine transparent liquid, no precipitates No. 19pyrrolidonecarboxylic transparent liquid, no precipitates acid No. 20N-acetylglycine transparent liquid, no precipitates No. 21N-acetyl-L-tyrosine transparent liquid, no precipitates No. 22 sodiumL-asparagate transparent liquid, no precipitates No. 23 sodiumL-glutamate transparent liquid, no precipitates No. 24 citrullinetransparent liquid, no precipitates No. 25 phenylalanine transparentliquid, no precipitates No. 26 glycineamide transparent liquid, noprecipitates Comparative none yellow orange precipitates Example 1

As shown by the results in Table 1, precipitates were formed in theantimicrobial composition of Comparative Example 1 which contained5-chloro-2-methyl-4-isothiazoline-3-one and2-methyl-4-isothiazoline-3-one but did not contain the aminocarboxylicacid represented by general formula [3] or the derivative thereof afterthe composition was left standing at the room temperature for one month.In contrast, the antimicrobial compositions of Example 1 which containedthe aminocarboxylic acid represented by general formula [3] or thederivative thereof showed no change in the appearance after thecompositions were left standing at the room temperature for one monthand exhibited excellent stability for a long time.

Example 2

From the 26 types of antimicrobial compositions prepared in Example 1,23 types of compositions were selected and left standing in a constanttemperature oven kept at 60° C. for 48 hours. Then, the content of5-chloro-2-methyl-4-isothiazoline-3-one was measured in accordance withthe high performance liquid chromatography and the residue wascalculated. The residue of 5-chloro-2-methyl-4-isothiazoline-3-one inthe antimicrobial composition containing glycine was 76%. The residuesof other antimicrobial compositions are shown in Table 2.

Comparative Example 2

The antimicrobial composition prepared in Comparative Example 1 was leftstanding in a constant temperature oven kept at 60° C. for 48 hours.Then, the content of 5-chloro-2-methyl-4-isothiazoline-3-one wasmeasured in accordance with the high performance liquid chromatography.No peaks of 5-chloro-2-methyl-4-isothiazoline-3-one were found in thechromatogram. This shows that 5-chloro-2-methyl-4-isothiazoline-3-onewas completely decomposed.

Comparative Example 3

An ethylene glycol solution (ZONEN-F; manufactured by ICHIKAWA GOSEIKAGAKU Co., Ltd.) containing 11% by weight of5-chloro-2-methyl-4-isothiazoline-3-one and 1% by weight of2-methyl-4-isothiazoline-3-one in an amount of 5.0 parts by weight, 2.0parts by weight of polylysine and 93.0 parts by weight of water weremixed to form a homogeneous solution and an antimicrobial compositionwas prepared.

The antimicrobial composition prepared above was left standing in aconstant temperature oven kept at 60° C. for 48 hours. Then, the contentof 5-chloro-2-methyl-4-isothiazoline-3-one was measured in accordancewith the high performance liquid chromatography. No peaks of5-chloro-2-methyl-4-isothiazoline-3-one were found in the chromatogram.This shows that 5-chloro-2-methyl-4-isothiazoline-3-one was completelydecomposed.

The results of Example 2 and Comparative Examples 2 and 3 are shown inTable 2.

TABLE 2 residual 5-chloro-2-methyl- Aminocarboxylic acid or4-isothiazoline-3-one derivative thereof (%) Example 1 No. 1 glycine 76No. 2 alanine 60 No. 3 β-alanine 58 No. 4 DL-serine 71 No. 5DL-threonine 76 No. 6 DL-asparagine 67 No. 7 L-glutamine 78 No. 8sarcosine 60 No. 9 DL-β-aminobutyric acid 73 No. 10 γ-aminobutyric acid61 No. 11 DL-methionine 45 No. 12 iminodiacetic acid 99 No. 13glycylglycine 100 No. 14 glycylglycylglycine 100 No. 15glycylglycylglycylglycine 100 No. 16 glycyl-L-glutamine 100 No. 17L-alanyl-L-glutamine 100 No. 18 β-alanyl-L-histidine 88 No. 19pyrrolidonecarboxylic acid 52 No. 20 N-acetylglycine 35 No. 21N-acetyl-L-tyrosine 62 No. 22 sodium L-asparagate 68 No. 23 sodiumL-glutamate 74 Comparative none 0 Example 2 Comparative polylysine 0Example 3

As shown by the results in Table 2,5-chloro-2-methyl-4-isothiazoline-3-one was completely decomposed in theantimicrobial composition of Comparative Example 2 which contained5-chloro-2-methyl-4-isothiazoline-3-one and2-methyl-4-isothiazoline-3-one but did not contain the aminocarboxylicacid represented by general formula [3] or the derivative thereof afterthe composition was left standing at 60° C. for 48 hours. In contrast,the antimicrobial compositions of Example 2 which contained theaminocarboxylic acid represented by general formula [3] or thederivative thereof showed a great residue of5-chloro-2-methyl-4-isothiazoline-3-one after the compositions were leftstanding at 60° C. for 48 hours and exhibited excellent heat stability.In particular, 5-chloro-2-methyl-4-isothiazoline-3-one was notdecomposed at all and the residue remained at 100% in the antimicrobialcompositions containing glycylglycine, glycylglycylglycine,glycylglycylglycylglycine, glycyl-L-glutamine or L-alanyl-L-glutamine,i.e., the compound having a structure in which the aminocarboxylic acidsrepresented by general formula [3] were bonded to each other through apeptide bond. The antimicrobial composition of Comparative Example 3containing a compound having a structure which is close to theaminocarboxylic acid represented by general formula [3] but in which thegroup represented by R⁴ is an alkyl group substituted with amino group,i.e., polylysine, showed inferior heat stability and5-chloro-2-methyl-4-isothiazoline-3-one was completely decomposed afterthe composition was left standing at 60° C. for 48 hours.

Example 3

An aqueous solution (KATHON-WT; manufactured by ROHM & HAAS Company)containing 11% by weight of 5-chloro-2-methyl-4-isothiazoline-3-one, 3%by weight of 2-methyl-4-isothiazoline-3-one, magnesium chloride andmagnesium nitrate was used in place of the ethylene glycol solution(ZONEN-F; manufactured by ICHIKAWA GOSEI KAGAKU Co., Ltd.) containing11% by weight of 5-chloro-2-methyl-4-isothiazoline-3-one and 1% byweight of 2-methyl-4-isothiazoline-3-one. Glycylglycine,glycylglycylglycine, glycylglycylglycylglycine, glycyl-L-glutamine orL-alanyl-L-glutamine was used as the aminocarboxylic acid represented bygeneral formula [3] or the derivative thereof Five types ofantimicrobial compositions were prepared in accordance with the sameprocedures as those conducted in Example 2. The prepared compositionswere left standing in a constant temperature oven kept at 60° C. for 48hours. Then, the content of 5-chloro-2-methyl-4-isothiazoline-3-one wasmeasured in accordance with the high performance liquid chromatography.

The residue of 5-chloro-2-methyl-4-isothiazoline-3-one was 100% in allcompositions.

Comparative Example 4

An aqueous solution (KATHON-WT; manufactured by ROHM & HAAS Company)containing 11% by weight of 5-chloro-2-methyl-4-isothiazoline-3-one, 3%by weight of 2-methyl-4-isothiazoline-3-one, magnesium chloride andmagnesium nitrate in an amount of 5 parts by weight and 95.0 parts byweight of water were mixed to form a homogeneous solution and anantimicrobial composition was prepared.

The prepared compositions were left standing in a constant temperatureoven kept at 60° C. for 48 hours. Then, the content of5-chloro-2-methyl-4-isothiazoline-3-one was measured in accordance withthe high performance liquid chromatography. The residue of5-chloro-2-methyl-4-isothiazoline-3-one was 51%.

The results of Example 3 and Comparative Example 4 are shown in Table 3.

TABLE 3 residual 5-chloro-2-methyl- Aminocarboxylic acid or4-isothiazoline-3-one derivative thereof (%) Example 3 No. 13glycylglycine 100 No. 14 glycylglycylglycine 100 No. 15glycylglycylglycylglycine 100 No. 16 glycyl-L-glutamine 100 No. 17L-alanyl-L-glutamine 100 Comparative none 51 Example 4

As shown by the results in Table 3,5-chloro-2-methyl-4-isothiazoline-3-one in the antimicrobialcompositions of Example 3 containing glycylglycine, glycylglycylglycine,glycylglycylglycylglycine, glycyl-L-glutamine or L-alanyl-L-glutamine,i.e., the compound in which the aminocarboxylic acids represented bygeneral formula [3] were bonded to each other through a peptide bond,was not decomposed at all and the residue remained at 100% after thecompositions were left standing at 60° C. for 48 hours. In contrast, theantimicrobial composition of Comparative Example 4 which did not containthe aminocarboxylic acid represented by general formula [3] or thederivative thereof showed inferior heat stability and about a half ofthe amount of 5-chloro-2-methyl-4-isothiazoline-3-one was decomposedafter the composition was left standing at 60° C. for 48 hours.

Example 4

An ethylene glycol solution (ZONEN-F; manufactured by ICHIKAWA GOSEIKAGAKU Co., Ltd.) containing 11% by weight of5-chloro-2-methyl-4-isothiazoline-3-one and 1% by weight of2-methyl-4-isothiazoline-3-one in an amount of 5.0 parts by weight, 1.09parts by weight of glycylglycine and 93.91 parts by weight of water weremixed to form a homogeneous solution and an antimicrobial compositionwas prepared. The prepared antimicrobial composition containedglycylglycine in an amount by mol twice the total amount by mol of5-chloro-2-methyl-4-isothiazoline-3-one and2-methyl-4-isothiazoline-3-one. Using Bacilus subtillus, the preparedcomposition was examined with respect to the effect of suppressinggrowth of the bacteria.

Into a liquid medium containing 1 g/liter of peptone and 1 g/liter ofyeast extract and having pH of 7, Bacilus subtillus was inoculated in anamount of 10⁶ bacteria/ml. To the inoculated medium, the aboveantimicrobial composition was added in an amount such that theconcentration was 20 mg/liter, 60 mg/liter or 100 mg/liter. The obtainedmedium was cultured at 30° C. for 24 hours while being shaken. Theeffect of suppressing growth of the bacteria was found when theconcentration was 60 mg/liter and 100 mg/liter although the effect wasnot found when the concentration was 20 mg/liter.

After the above antimicrobial composition was left standing at the roomtemperature for one month, the composition was examined with respect tothe effect of suppressing growth of the bacteria in accordance with thesame procedures as those conducted above. The effect of suppressinggrowth of the bacteria was found when the concentration was 60 mg/literand 100 mg/liter although the effect was not found when theconcentration was 20 mg/liter.

Comparative Example 5

An ethylene glycol solution (ZONEN-F; manufactured by ICHIKAWA GOSEIKAGAKU Co., Ltd.) containing 11% by weight of5-chloro-2-methyl-4-isothiazoline-3-one and 1% by weight of2-methyl-4-isothiazoline-3-one in an amount of 5.0 parts by weight and95 parts by weight of water were mixed to form a homogeneous solutionand an antimicrobial composition was prepared. Using Bacilus subtillus,the prepared composition was examined with respect to the effect ofsuppressing growth in accordance with the same procedures as thoseconducted in Example 4. The effect of suppressing growth of the bacteriawas found when the concentration was 60 mg/liter and 100 mg/literalthough the effect was not found when the concentration was 20mg/liter.

After the above antimicrobial composition was left standing at the roomtemperature for one month, the composition was examined with respect tothe effect of suppressing growth of the bacteria in accordance with thesame procedures as those above. The effect of suppresing growth of thebacteria was not found in any of the cases where the concentration was20 mg/liter, 60 mg/liter, and 100 mg/liter.

The results of Example 4 and Comparative Example 5 are shown in

TABLE 4 concentration of antimicrobial effect of suppressing compositiongrowth of time of test (mg/liter) the bacteria Example 4 immediatelyafter preparation 20 not exhibited 60 exhibited 100 exhibited after 1month at room temp. 20 not exhibited 60 exhibited 100 exhibitedComparative Example 5 immediately after preparation 20 not exhibited 60exhibited 100 exhibited after 1 month at room temp. 20 not exhibited 60not exhibited 100 not exhibited

As shown by the results in Table 4, the antimicrobial compositionprepared in Comparative Example 5 lost effect of suppressing growth ofBacillus subtillus after the composition was left standing at the roomtemperature for one month. In contrast, the antimicrobial compositionprepared in Example 4 which contained glycylglycine held the effect ofsuppressing growth of the bacteria after the composition was leftstanding at the room temperature for one month. Thus, it is shown thatthe antimicrobial composition of the present invention exhibitsexcellent stability for a long time.

Example 5

Glycine, sodium L-glutamate, iminodiacetic acid or glycylglycine wasused as the aminocarboxylic acid represented by general formula [3] orthe derivative thereof. An ethylene glycol solution (ZONEN-F;manufactured by ICHIKAWA GOSEI KAGAKU Co., Ltd.) containing 11% byweight of 5-chloro-2-methyl-4-isothiazoline-3-one and 1% by weight of2-methyl-4-isothiazoline-3-one in an amount of 5.0 parts by weight, theaminocarboxylic acid represented by general formula [3] or thederivative thereof in an amount by mol twice the total amount by mol of5-chloro-2-methyl-4-isothiazoline-3-one and2-methyl-4-isothiazoline-3-one and water in an amount such that thetotal amount of the composition was 100.0 parts by weight were mixed toform a homogeneous solution and 4 types of antimicrobial compositionswere prepared.

The above test of irritation of skin was conducted using the preparedantimicrobial compositions.

Comparative Example 6

An ethylene glycol solution (ZONEN-F; manufactured by ICHIKAWA GOSEIKAGAKU Co., Ltd.) containing 11% by weight of5-chloro-2-methyl-4-isothiazoline-3-one and 1% by weight of2-methyl-4-isothiazoline-3-one in an amount of 5.0 parts by weight and95.0 parts by weight of water were mixed to form a homogeneous solutionand an antimicrobial composition was prepared.

The above test of irritation of skin was conducted using the preparedantimicrobial composition.

The results of Example 5 and Comparative Example 6 are shown in Table 5.

TABLE 5 amino- number obtained by evaluation primary index carboxylictime (hour) for skin acid irritation 1 24 48 72 irritation Example 5glycine erythema 2.33 2.33 2.67 3.33 5.67 edema 4.00 3.00 3.00 2.00total 6.33 5.33 5.67 5.33 sodium erythema 2.33 2.33 2.67 3.33 5.67L-glutamate edema 4.00 3.00 3.00 2.00 total 6.33 5.33 5.67 5.33iminodiacetic erythema 2.33 3.00 2.67 3.33 5.42 acid edema 4.00 2.332.00 2.00 total 6.33 5.33 4.67 5.33 glycylglycine erythema 2.00 2.672.67 2.67 5.25 edema 4.00 2.67 2.33 2.00 total 6.00 5.34 5.00 4.67Comparative Example 6 none erythema 3.33 3.00 3.33 3.33 7.25 edema 4.004.00 4.00 4.00 total 7.33 7.00 7.33 7.33

The results of Example 5 and Comparative Example 6 in Table 5 wereobtained under the same condition except that the aminocarboxylic acidor the derivative thereof was present in Example 5 and absent inComparative Example 6. When these results are compared, it is shown thatthe antimicrobial compositions prepared in Example 5 which containedglycine, sodium L-glutamate, iminodiacetic acid or glycylglycine showedsmaller primary indices of skin irritation than the antimicrobialcomposition prepared in Comparative Example 6 which did not contain theaminocarboxylic acid or the derivative thereof. Thus, it is shown thatirritation of skin caused by the antimicrobial composition containingthe isothiazolone compound was reduced when the composition containedthe aminocarboxylic acid or the derivative thereof

INDUSTRIAL APPLICABILITY

The antimicrobial composition of the present invention comprises theisothiazolone compound and the aminocarboxylic acid or the derivativethereof, shows excellent stability for a long time and excellent heatstability, suppresses decomposition of the isothiazolone compound evenafter storage for a long time, exhibits the excellent antimicrobialeffect of the isothiazolone compound, reduces irritation of skin causedby the isothiazolone compound and can be handled easily.

What is claimed is:
 1. An antimicrobial composition consistingessentially of (i) 0.5 to 8% by weight of an isothiazolone compoundselected from the group consisting of a compound of the followingformula [1] and a compound of the following formula [2], and (ii) anaminocarboxylic acid of the following formula [3], the aminocarboxylicacid being in an amount of moles of 0.1 to 50 times the amount of molesof the isothiazolone compound, the isothiazolone compound and theaminocarboxylic acid both being dissolved in a solvent of water andoptionally a hydrophilic solvent;

wherein R¹ represents a hydrogen atom, an alkyl group, an alkenyl group,an alkynyl group or an aralkyl group, X and Y each represents a hydrogenatom or a halogen atom or form a benzene ring in combination with carbonatoms at the 4- and 5-positions of the isothiazolone compound, Mrepresents a cation of an alkali metal, an alkaline earth metal, a heavymetal or an amine, Z represents an anion forming, in combination withthe cation represented by M, a compound having a sufficient solubilityto form a complex compound, a represents 1 or 2 and n represents aninteger required for the anion represented by Z to satisfy a valence ofthe cation represented by M;

wherein R² represents a hydrogen atom or an alkyl group having 1 to 5carbon atoms unsubstituted or substituted with a carboxyl group, R³represents a linear or branched alkylene group having 1 to 5 carbonatoms, R⁴ represents a hydrogen atom or an alkyl group having 1 to 5carbon atoms unsubstituted or substituted with a carboxyl group, acarbamoyl group, a hydroxyl group, a phenyl group, a hydrophenyl group,an ureido group, a methylthio group or a 4-imidazolyl group, R² and R⁴form a heterocyclic group unsubstituted or substituted with a hydroxylgroup or an oxo group in combination with N—(R³)_(b)—C and b represents0 or
 1. 2. An antimicrobial composition consisting essentially of (i)0.5 to 8% by weight of an isothiazolone compound selected from the groupconsisting of the compound of the formula [1] according to claim 1 andthe compound of the formula [2] according to claim 1 and (ii) anaminocarboxylic acid compound selected from the group consisting of (a)a metal salt of the aminocarboxylic acid of the formula [3] according toclaim 1; (b) a compound having a structure in which aminocarboxylicacids of said formula [3] are bonded to each other through a peptidebond or a metal salt of the compound; (c) a compound having a structurein which the aminocarboxylic acid of said formula [3] is bonded to adifferent aminocaboxylic acid through a peptide bond or a metal salt ofthe compound; (d) an N-acetyl compound of the aminocarboxylic acid ofsaid formula [3] or a metal salt of the compound; and (e) an amide ofthe aminocarboxylic acid of said formula [3], the aminocarboxylic acidcompound being in an amount of moles of 0.1 to 50 times the amount ofmoles of the isothiazolone compound, the isothiazolone compound and theaminocarboxylic acid compound both being dissolved in a solvent of waterand optionally a hydrophilic solvent.
 3. An antimicrobial compositionaccording to claim 1, wherein the aminocarboxylic acid of the formula[3] is in an amount of moles of 1 to 10 times the amount by moles of theisothiazolone compound.
 4. An antimicrobial composition according toclaim 1, wherein the isothiazolone compound of the formula [1] or theisothiazolone compound of the formula [2] and the aminocarboxylic acidof the formula [3] are dissolved in a mixed solvent of water and ahydrophilic solvent.
 5. An antimicrobial composition according to claim1, wherein the isothiazolone compound is of the formula [1] and is5-chloro-2-methyl-4-isothiazoline-3-one.
 6. An antimicrobial compositionaccording to claim 1, wherein the isothiazolone compound is of theformula [2] and is a complex compound of5-chloro-2-methyl-4-isothiazoline-3-one with magnesium chloride ormagnesium nitrate.
 7. An antimicrobial composition according to claim 1,wherein the aminocarboxylic acid of the formula [3] is glycine.
 8. Anantimicrobial composition according to claim 1, wherein theaminocarboxylic acid of the formula [3] is iminodiacetic acid.
 9. Anantimicrobial composition according to claim 2, wherein theaminocarboxylic acid compound is glycylglycine.
 10. An antimicrobialcomposition according to claim 2, wherein the aminocarboxylic acidcompound is glycylglycylglycine.
 11. An antimicrobial compositionaccording to claim 2, wherein the aminocarboxylic acid compound isglycyl-L-glutamine.
 12. An antimicrobial composition according to claim2, wherein the aminocarboxylic acid compound is L-alanyl-L-glutamine.13. An antimicrobial composition according to claim 2, wherein theaminocarboxylic acid compound is β-alanyl-L-histidine.
 14. Anantimicrobial composition according to claim 2, wherein theaminocarboxylic acid compound is sodium L-glutamate.
 15. A method forcombatting microbes comprising applying to microbes or to a locusthereof an antimicrobial amount of the antimicrobial compositionaccording to claim
 1. 16. A method for combatting slime in a systemselected from the group consisting of (a) a paper and pulp manufacturingsystem and (b) a cooling water system comprising applying to said systeman anti-slime effective amount of the antimicrobial compositionaccording to claim
 1. 17. An antimicrobial composition according toclaim 1, wherein the isothiazolone compound is selected from the groupconsisting of 2-methyl-4-isothiazoline-3-one,2-ethyl-4-isothiazoline-3-one, 2-octyl-4-isothiazoline-3-one,5-chloro-2-methyl-4-isothiazoline-3-one,5-chloro-2-octyl-4-isothiazoline-3-one,4,5-dichloro-2-methyl-4-isothiazoline-3-one,4,5-dichloro-2-octyl-4-isothiazoline-3-one and1,2-benzoisothiazoline-3-one; and the aminocarboxylic acid is selectedfrom the group consisting of glycine, alanine, β-alanine, valine,leucine, isoleucine, serine, threonine, asparagic acid, glutamic acid,asparagine, glutamine, sarcosine, citrulline, methionine, α-aminobutyricacid, β-aminobutyric acid, γ-aminobutyric acid, ε-aminocaproic acid,phenylalanine, tyrosine, histidine, proline, 4-hydroxyproline,2-pyrrolidine-5-carboxylic acid and iminodiacetic acid.
 18. Anantimicrobial composition according to claim 2, wherein the isothiazlonecompound is selected from the group consisting of2-methyl-4-isothiazoline-3-one, 2-ethyl-4-isothiazoline-3-one,2-octyl-4-isothiazoline-3-one, 5-chloro-2-methyl-4-isothiazoline-3-one,5-chloro-2-octyl-4-isothiazoline-3-one,4,5-dichloro-2-methyl-4-isothiazoline-3-one,4,5-dichloro-2-octyl-4-isothiazoline-3-one and1,2-benzoisothiazoline-3-one; and the aminocarboxylic acid is selectedfrom the group consisting of glycylglycine, glycylglycylglycine,glycylglycylglycylglycine, glycylalanine, glycylasparagine,glycylleucine, glycylisoleucine, glycylphenylalanine, glycylproline,glycylsarcosine, glycylserine, glycylthreonine, glycylvaline,glycylglutamine, alanylalanine, alanylasparagine, alanylglutamine,alanylglycine, alanylphenylalanine, alanylthyrosine, β-alanylhistidine,polyasparagic acid, polyglutamic acid, N-acetylglycine, N-acetylalanine,N-acetyl-L-asparagic acid, N-acetyl-L-glutamic acid, N-acetyltyrosineand glycineamide.
 19. A method for suppressing the decomposition of asolution consisting essentially of an isothiazolone compound in anaqueous solution or in a mixed solution of water and a hydrophilicsolvent and for reducing skin irritation caused by the solution of theisothiazolone compound comprising adding to the solution an effectiveamount of a compound consisting essentially of an aminocarboxylic acidof the following formula [3]:

wherein R² represents a hydrogen atom or an alkyl group having 1 to 5carbon atoms unsubstituted or substituted with a carboxyl group, R³represents a linear or branched alkylene group having 1 to 5 carbonatoms, R⁴ represents a hydrogen atom or an alkyl group having 1 to 5carbon atoms unsubstituted or substituted with a carboxyl group, acarbamoyl group, a hydroxyl group, a phenyl group, a hydrophenyl group,an ureido group, a methylthio group or a 4-imidazolyl group, R² and R⁴form a heterocyclic group unsubstituted or substituted with a hydroxylgroup or an oxo group in combination with N—(R³)_(b)—C and b represents0 or
 1. 20. An antimicrobial composition consisting essentially of (i)0.5 to at by weight of an isothiazolone compound selected from the groupconsisting of a compound of the following formula [1] and a compound ofthe following formula [2], (ii) an aminocarboxylic acid of the followingformula [3], and (iii) at least one substance selected from the groupconsisting of a corrosion inhibitor, a scale inhibitor, an antimicrobialagent other than an isothiazolone compound, a defoaming agent, asurfactant and an algicide, the aminocarboxylic acid being in an amountof moles of 0.1 to 50 times the amount of moles of the isothiazolonecompound, the isothiazolone compound and the aminocarboxylic acid bothbeing dissolved in a solvent of water and optionally a hydrophilicsolvent:

wherein R¹ represents a hydrogen atom, an alkyl group, an alkenyl group,an alkynyl group or an aralkyl group, X and Y each represents a hydrogenatom or a halogen atom or form a benzene ring in combination with carbonatoms at the 4- and 5-positions of the isothiazolone compound, Mrepresents a cation of an alkali metal, an alkaline earth metal, a heavymetal or an amine, Z represents an anion forming, in combination withthe cation represented by M, a compound having a sufficient solubilityto form a complex compound, a represents 1 or 2 and n represents aninteger required for the anion represented by Z to satisfy a valence ofthe cation represented by M;

wherein R² represents a hydrogen atom or an alkyl group having 1 to 5carbon atoms unsubstituted or substituted with a carboxyl group, R³represents a linear or branched alkylene group having 1 to 5 carbonatoms, R⁴ represents a hydrogen atom or an alkyl group having 1 to 5carbon atoms unsubstituted or substituted with a carboxyl group, acarbamoyl group, a hydroxyl group, a phenyl group, a hydrophenyl group,an ureido group, a methylthio group or a 4-imidazolyl group, R² and R⁴form a heterocyclic group unsubstituted or substituted with a hydroxylgroup or an oxo group in combination with N—(R³)_(b)—C and b represents0 or
 1. 21. An antimicrobial composition consisting essentially of (i)0.1 to 10% by weight of an isothiazolone compound selected from thegroup consisting of a compound of the following formula [1] and acompound of the following formula [2], (ii) 0.1 to 20% by weight of theaminocarboxylic acid of the following formula [3], and (iii) 0 to 50% byweight of a corrosion inhibitor, 0 to 50% by weight of a scaleinhibitor, 0 to 30% by weight of an antimicrobial agent other than anisothiazolone compound, 0 to 10% by weight of a defoaming agent, 0 to10% by weight of a surfactant, 0 to 10% by weight of an algicide and 30to 99% by weight of water or a hydrophilic organic solvent;

wherein R¹ represents a hydrogen atom, an alkyl group, an alkenyl group,an alkynyl group or an aralkyl group, X and Y each represents a hydrogenatom or a halogen atom or form a benzene ring in combination with carbonatoms at the 4- and 5-positions of the isothiazolone compound, Mrepresents a cation of an alkali metal, an alkaline earth metal, a heavymetal or an amine, Z represents an anion forming, in combination withthe cation represented by M, a compound having a sufficient solubilityto form a complex compound, a represents 1 or 2 and n represents aninteger required for the anion represented by Z to satisfy a valence ofthe cation represented by M;

wherein R² represents a hydrogen atom or an alkyl group having 1 to 5carbon atoms unsubstituted or substituted with a carboxyl group, R³represents a linear or branched alkylene group having 1 to 5 carbonatoms, R⁴ represents a hydrogen atom or an alkyl group having 1 to 5carbon atoms unsubstituted or substituted with a carboxyl group, acarbamoyl group, a hydroxyl group, a phenyl group, a hydrophenyl group,an ureido group, a methylthio group or a 4-imidazolyl group, R² and R⁴form a heterocyclic group unsubstituted or substituted with a hydroxylgroup or an